JPS6140838A - Sio2-b2o3 series glass and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the SiO2-B2O3 series glass which is useful as the intermediate raw material of electronic material requiring high purity and high functional characteristics by adding B2O3 (a precursor) to the high-purity hydrated silica gel, drying the mixture and thereafter heating and melting it. CONSTITUTION:The silica sol obtained by purifying an aq. alkali silicate soln. with an ion exchange resin is changed to silica gel and the silica gel is pickled to obtain the high-purity hydrated silica gel which has <=10ppb alpha-radiator as (U+Th) per SiO2 and <=10ppb ionic impurities such as Na and Cl. B-contg. hydrated silica gel of 0.5-10wt% water content and 1-100mum average particle size is obtained by adding 1-10wt% (expressed in terms of B2O3) B2O3 or its precursor (e.g. trimethyl borate) per SiO2 to the silica gel and drying the mixture. Then the hydrated silica gel is heated and melted to obtain B-contg. silica glass having <=100mus/cm electric conductance of extracted water which is obtained by boiling and leaching of glass, >=80% degree of melting and 1-100mum average particle size.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a raw material for high-purity fused spherical silica glass and a method for producing fused spherical silica glass using the same.

More specifically, fillers for resin encapsulation of semiconductors, abrasive materials,
The present invention relates to a method for producing high-purity hydrated silica and anhydrous silica, which can be used as intermediate raw materials for electronic materials that require high purity and high functionality, such as substrates and package materials.

Conventional technology A large amount of inorganic fillers are used in the resin encapsulation of semiconductors, and these are mainly known as crystalline silica, which is a crushed product of natural quartz, and fused silica, which is made by melting this at high temperatures in an oxyhydrogen flame. .

Recently, quality characteristics requirements for encapsulants have become even stricter, especially due to the high integration of semiconductors. and (3) reduction of ionic impurities. In order to cope with these problems, using silica obtained by conventional crushing and/or melting of natural quartz as a filler has economical problems such as purity and securing the quantity of resources, and it is not always necessary to use silica in a stable state. However, it has become necessary to use a new synthetic silica.

In response to this, a method has recently been proposed in which silica glass powder is produced by reacting a silicate such as alkali silicate with mineral acid at a hydrogen ion concentration of less than i, s to precipitate hydrated silicic acid, followed by washing, drying, and firing. (Unexamined Japanese Patent Application Publication No. 1989)
On the other hand, there is a method for producing fine powder silica containing boron oxide, which is characterized by oxidizing and burning a mixture of a specific organosilicon compound and an organoboronant compound. zs-tatio issue).

However, this method not only does not disclose the amount of α-radioactive substances and other impurities, but also has problems such as the fact that the cost of using an organosilicon compound as a silica source is extremely high compared to when sodium silicate is used as a silica source. There's a problem.

Problems to be Solved by the Invention The present invention uses an aqueous alkali silicate solution as a silica source, and purifies hydrated silica obtained from this by an ion exchange method or an acid neutralization method, and then heats and melts it to obtain α-emitter-containing silica. The object of the present invention is to industrially advantageously produce a small amount of high-purity silica-based glass. However, what is important in this production method is not only how to prepare high-purity hydrated silica, but also how to reduce the thermal energy consumption of the obtained hydrated silica.

The present inventors have already found several solutions to methods for producing high-purity hydrated silica using an aqueous alkali silicate solution.

Very strict quality characteristics are required for silica as a filler for resin sealing, and the manufacturing conditions must also be extremely limited.

The inventors of the present invention have conducted extensive research in view of the problem of sloping, and have found that high-purity hydrated silica gel in which a boron compound is present and heated and melted can be used not only to reduce energy consumption but also to be used for resin sealing. The present invention was completed based on the finding that the material satisfactorily meets the quality characteristics required for a filler.

Means for Solving the Problems The present invention provides that the boron content is B2O based on the total weight of the glass.
SiO2-B2O3, characterized in that it is boron-containing silica glass with 1 to 10% by weight as 8, α-radiator is 10 ppb or less as U+Th, and the electric conductivity of the extracted water obtained by boiling and leaching the glass is iooμB/cm or less. The present invention relates to glass and a method for producing the same.

The SiO2-B2O3 glass according to the present invention has the above-mentioned properties because it is indispensable as a resin encapsulant for semiconductors. Particularly preferably U and Th
is less than/ppb and the above electrical conductivity is goμ
Highly integrated LE3X and V should be less than θ/clIL.
This is necessary in view of the possibility of malfunction due to soft errors when used as a sealing material for LBX.

Here, the value of electrical conductivity is 70% when the sample is dispersed in pure water.
The extracted water obtained by boiling the weight% slurry for 6 hours was used as the sample.
It is determined as electrical conductivity at 5°C, and serves as a measurement index for the content of ionic impurities such as alkali or chlorine.

SiO□-B2O. according to the present invention. Glasses are preferably in the form of ingots or powders, or because they are used for many purposes as fillers for resins, they are preferably in the form of powders of 400 μm or less, with an average particle size in the range of 1 to 700 μm. , 5~! Something in the 0μ door range is best.

Particle size distribution here means the value shown when measured with a Coulter counter.

Further, the above-mentioned glass refers to a case where the degree of melting is equal to or higher than goqb, and the degree of melting is expressed by the total number of particles in the field of view of a microscope using the following formula. In this case, it is desirable that the field of view of the microscope is at least larger than the field of view, and that at least 50 or more particles can be detected in the field of view.

The meltability of particles can be easily distinguished by microscopic observation, depending on whether or not they are transparent as glass.

Boron-containing high-purity silica glass having such characteristics is a new substance, and is particularly suitable as a filler for resin compounds for Kopa Shio-Zage.

SiO□-B2O. according to the present invention. The system glass is made by adding boron oxide or its precursor to high-purity hydrated silica gel obtained from alkali silicate as raw material (S10!). Hit B2O. 1 in conversion
It can be produced by heating and melting the dried boron-containing hydrous silica gel after addition of ~10% by weight.

As long as the silica source which is the main raw material of the present invention is a high purity hydrous silica gel obtained from an alkali silicate as a raw material, there is no particular limitation on the method of producing it from an alkali silicate.

The most preferable method is, for example, when an aqueous alkali silicate solution is purified by a purification method using an ion exchange resin to form a silica gel through a silica sol, and this gel is acid-washed with an acid such as nitric acid. There are methods such as adding an aqueous solution to precipitate silica gel and similarly acid-washing. Such high-purity hydrated silica gel contains α-
The content of the radiator must be 10 ppb or less as U-)-Th, preferably /ppb or less, and the content of ionic impurities such as sodium or chlorine must be /Oppb or less.

On the other hand, boron oxide or its precursor is used as a boron source, but the precursor here is a compound that becomes only boron oxide when heated and other components are volatilized by heat, and the compound is water-soluble. Refers to something that is sexual. Examples of such compounds include boric acid, various ammonium borates, and organic borate esters such as trimethyl borate and triethyl borate. It has to be something.

Both raw materials are uniformly mixed in a range of 1 to 70% by weight of B2O3 relative to SiO2.

The reason for this is that the amount of boron oxide or its precursor added is
In contrast to 2, if B2O3 is less than 7% by weight, the addition effect on melting is poor, and on the other hand, i.

If it is more than % by weight, the melting point will drop significantly and melting will become easier, but the electrical conductivity of the extract will tend to increase and the true specific gravity will also decrease.

Therefore, it is necessary to use the boron source within the above range, and more preferably 2 to 3 weight percent.

There are no particular limitations on the mixing of the silica source and boron source, and any desired method may be used to achieve as uniform a mixture as possible, but usually the above-mentioned hydrated silica gel is mixed with a water-soluble boron compound in water beforehand. A uniform slurry of boron-containing silica is prepared by dispersing the boron-containing aqueous solution, or by adding and dissolving a water-soluble boron compound to a slurry of silica gel dispersed in water. As another method, an aqueous solution of a boron compound may be added to a filter cake of high-purity hydrous silica gel, and a uniform mixture may be prepared by impregnating or kneading without forming a slurry.

Such a mixture is then dehydrated and dried, and when drying from a slurry state, spray drying is the most effective and preferred method.

The reason for this is that a feed material with uniform particle size distribution and good fluidity that can be effectively used in the next melting process can be prepared all at once.

Another method is to dry the boron-containing impregnated or kneaded product using a desired dryer such as a rotary dryer or a stationary dryer.

In this case, depending on the purpose of the product, the dry product may be pulverized into a powder to be used as a supply body for melting, or it may be used as is for ingots that are melted in a desired size and shape. Note that the purpose of drying boron-containing silica gel is to effectively dehydrate it to be supplied to the next melting process, so the degree of dehydration depending on the melting method is not uniform, but in most cases, the water content is A range of 1 to 10% by weight, particularly 2 to 7% by weight, is most preferred. The reason for this is that if /wt% is not grooved, particles may adhere to the feed port during melting due to the charged nature of the particles in the powder supply body, resulting in poor fluidity; This is because a foaming phenomenon of the molten material is observed.

Note that in the present invention, the moisture content refers to the moisture content of the sample at 600%
It is expressed as a value calculated from the loss on heating after baking at ℃ for 7 hours.

The dried boron-containing silica gel thus obtained is melted in a desired melting furnace. Examples of melting furnaces include Acheson furnace,
An electric furnace such as an arc furnace or an oxy-fuel gas furnace can be applied, but heating and melting using oxyhydrogen is preferable in view of the contamination of impurities and the appearance of the product.

In the present invention, flame melting is the most preferable method of melting using powder as a feeder, and this method will be explained below.

This melting operation involves melting the boron-containing silica gel particles by continuously supplying the boron-containing silica gel particles to a predetermined flame section such as an oxygen-hydrogen flame, an oxygen-acetylene flame, an oxygen-propane flame, or a plasma flame. This flame melting operation itself is a technique that has long been known for melting inorganic powders.

Therefore, in order to flame-melt and mold boron-containing silica gel particles as a raw material to obtain, for example, spherical or elliptical fused silica with an average particle diameter of 1 to /θOμ, the flame length must be 30 cIIL or more at high temperature. Requires moderate flame conditions. When a burner that can be used for this purpose is an oxygen-fuel gas system, it is preferable that oxygen is injected from inside the burner, fuel gas is injected from a number of holes on the outside, and dehydrated silica is injected along with the oxygen gas.

In the case of plasma arc, the temperature of the arc part is significantly higher than in the oxygen-fuel gas system, so it can be processed without problems unless the amount of powder injected is excessive. Although it takes only a short time, it becomes substantially molten glass-like transparent spherical to elliptical particles with extremely good fluidity.

The obtained molten boron-containing silica particles are collected by a cyclone after cooling with a gas stream as necessary, or by wet recovery using water, etc. to obtain the high-purity boron-containing silica glass according to the present invention. You can get the product.

As described above, the method of the present invention enables industrially advantageous mass supply of high-purity fused silica particles as a filler for sealants that require high performance, rather than wet silica using an aqueous alkali silicate solution as a starting material. It is possible to do so.

Example The Atsushi invention will be explained below using examples.

Example / Sodium metasilicate hydrate was dissolved in water to give q% SiO
2, Hiromu, / An aqueous sodium silicate solution of % HalO was obtained. This diluted aqueous solution was previously converted into H-form with sulfuric acid and passed through a column filled with R-/2OB cation exchange resin manufactured by Organo Co., Ltd. for treatment.

The dilute silica sol solution with j The sample was treated with acid, washed with water, and treated with F.

Ammonium borate aqueous solution ((NH4) 1
1B2O110% by weight] was added (B, O,/S
iO2) approximately 3% by weight and S10! Content rate/j
-, 0% by weight of the slurry. In addition, after drying and firing at 20°C, chemical analysis and activation analysis revealed that B2O3 was 74% by weight and Ha2. t
pI)m,01/,coppm,UO,? pp
b or less, Tho, g ppb or less. This slurry is treated with a spray dryer that uses electrically heated hot air as a heat source to reduce the moisture content. , flathead boron-containing silica gel powder was obtained.

The burner used for flame melting has a primary oxygen nozzle of J■φ in the center of the burner, from which the raw material boron-containing silica powder is transported by oxygen, and on the outside thereof, fuel gas nozzles,
A secondary oxygen nozzle and fuel gas nozzle were provided. The combustion gas was treated with water spray using a venturi scrubber, and boron-containing fused spherical silica was recovered using a cyclone. In this example, the fuel gas is propane λθ1/&, -
As a result of processing with secondary oxygen for 301.7 minutes, secondary oxygen at 60 t/min, and amount of boron-containing silica powder added at 30%, spherical boron-containing silica was obtained which was almost completely melted and had a melting degree of 99%. .

The properties of this fused spherical boron-containing silica were as follows.

l average particle size and average particle size J, lt, 7μ door particle size distribution j-30μ door normal distribution Yu true specific gravity
x, og 3 chemical analysis value Element content (activation analysis value) B O, 92% by weight
Ha '1.4 ppm QJ, 0. g ppm U θ, ppb or less (Koj℃) i2. , jp/cm
Na+ 6. θsp
The boron-containing silica gel obtained in Example 1 was dried at 75θ°C in a stationary dryer instead of spray drying, and then pulverized. The material was classified using a 100 μm square sieve, and the portion with a size of 100 μm or less (moisture content: 1./weight) was subjected to flame melting treatment in the same manner as in Example 1. The properties of the fused spherical boron-containing silica thus obtained were as follows.

l Average particle size and average particle size 17.6 μm Particle size distribution Particle size distribution - normal distribution of ~ so μm 2 true ratio
Weight λ, Or 3 Chemical analysis values Element Content B 0.97% by weight Na ta, s ppm CA O, '7 ppm U θ, t ppb or less

Electrical conductivity (3℃) /b, 3μS Ma”
6. θ,? ppm0J--0.01ppm
The following pH melting rate: ioo% The same operation as in Comparative Example/Example/ was performed on the hydrous silica gel obtained in Example/ without the addition of ammonium borate aqueous solution. The following parts were spherical fused silica, but only the surface of the large particles was melted, retaining the shape before melting treatment, and the melting rate was only 5.0. Examine its bulk specific gravity. and/,/
kg/mlc (tap method), and was significantly bulkier than the bulk specific gravity of 13ag/ml obtained in Example. In order to achieve complete melting with a melting rate of 1 ootlb, the following melting conditions were required: propane 30 t/min, secondary oxygen 4'O 11 min, secondary oxygen/o ot 1 min, and silica addition amount 30 i/min.

Examples J-s and Comparative Examples In Example 1, a silica-containing solution obtained from No. 3 sodium silicate instead of the sodium metasilicate aqueous solution was subjected to ion exchange treatment, coagulation precipitation, and acid treatment in the same manner as in Example. A predetermined amount of ammonium borate aqueous solution was added to the silica gel obtained, and after kneading, it was dried in a stationary dryer for 75 minutes.
It was dried at θ°C to obtain a product with a water content of 3.3% by weight.

After pulverizing this, it was packed in an S0 crucible and heated in an electric furnace at a predetermined temperature for 2 hours to observe the melting tendency.

An edict, an example of /! When representative physical properties were measured for products obtained under 00°C melting conditions, the following results were obtained: O l average particle diameter and No. 9. /μm Particle size distribution Ko~! Normal distribution ratio of rθμm
Heavy 2. Og 3 Analysis Value Element Content B 3.18% by weight Na &, /ppm α Olzappm U /pp, ) or less Th Noppb or less Accidental water extraction test Electrical conductivity 1, Sμ8/pxt? o, o 3 ppm α - 0,07 ppm or less pH 5,, t Melting ratio 100 t Example 6 32 gr of HNO, /q, flathead nitric acid solution was placed in an RT reaction tank equipped with a stirrer and heated to 10°C. While stirring, add J Engineering S No. 3 sodium silicate (Na2O9.
2 Col:, A; %, Si%/NagO molar ratio 3. koθ
)ko100f! was added over about 30 minutes. The HNOs/Na,O molar ratio of the raw materials used in the reaction was 3.2/. During this time, the temperature of the reaction tank was maintained between 0 and 90°C. After adding the sodium silicate, the reaction slurry was heated at 90°C for 7 days.
Stir for hours. Through solid-liquid separation from the reaction-completed slurry,
Separate the silica precipitate, repulp the obtained silica with water, take the separated silica in a st tank with a stirrer, add water and nitric acid to it, make the entire slurry st,
The nitric acid concentration in the slurry was adjusted to IN, and the silica slurry was heated and acid-treated at 90° C. for 3 hours while stirring. Silica gel was separated from the slurry and washed with water to obtain high purity hydrous silica gel. Analysis of this silica gel revealed that Na: 2. ．． 3 ppm, U and T
h were both /ppb or less0 This silica gel was made into a slurry and triethylboron was added to S
10. Against B2O. After adding it to a concentration of -85% by weight, it was thoroughly mixed.

Next, a boron-containing silica gel having a moisture content of 3.5% by weight was prepared by spray drying in the same manner as in Example.

A boron-containing silica glass sphere was obtained by flame-melting the silica gel in the same manner as in Example 0. The physical properties of the obtained glass sphere were measured, and the results were as follows. Ta.

1 Average particle diameter / g-Aμm Particle size distribution - Normal distribution beside jθμ 2 True specific gravity 2.0 g 3 Analysis value Element Content B 5 da Weight % Na 2. / ppm α θ + sppm Both U and Th / ppb or less Kuji water extraction test electrical conductivity μs/cm Na + 0.62 ppm or less α - 0.07 ppm or less pH! Effects of the Invention The boron-containing silica glass according to the present invention can be used in the same manner as natural high-purity silica conventionally used as a filler for sealants. In particular, it can be manufactured from alkali silicate, and because it contains boron, thermal energy can be saved considerably in the melting process, and it also has a sufficient function as a filler, so it can be industrially advantageously supplied in large quantities. can.

Claims (1)

[Claims] 1. Boron content is 1 to 10% by weight as B_2O_3
, the α-radiator is 10 as U+Th relative to the total amount of glass.
SiO_2-B_2O_3-based glass, characterized in that it is a boron-containing silica glass in which the electric conductivity of extracted water obtained by boiling and leaching the glass is 100 μc/cm or less. 2. Boron-containing silica glass has an average particle size of 1 to 100μ
Si according to claim 1, which is a powder in the range of m
O_2-B_2O_3 glass. 3. SiO_2 according to claim 1 or 2, wherein the boron-containing silica glass has a melting degree of 80% or more
-B_2O_3 glass. 4. Add boron oxide or its precursor to high-purity hydrated silica gel obtained from alkali silicate as a raw material per SiO_2
A method for producing SiO_2-B_2O_3-based glass, which comprises heating and melting dried boron-containing hydrous silica gel after addition of 1 to 10% by weight in terms of_2O_3. 5. High purity silica gel has α-emitter U per SiO_2
The method for producing SiO_2-B_2O_3 glass according to claim 4, wherein +Th is 10 ppb or less and ionic impurities such as sodium and chlorine are 10 ppm or less. 6. SiO_2-B_2O_3 system according to claim 4, wherein the boric acid precursor is at least one or two or more water-soluble boron-containing compounds selected from boric acid, ammonium borate, and boric acid ester. Glass manufacturing method. 7. The method for producing SiO_2-B_2O_3 glass according to claim 4, wherein the boron-containing hydrous silica gel has a water content of 0.5 to 10% by weight. 8. Boron-containing hydrous silica gel has an average particle size of 1 to 100μ
The method for producing SiO_2-B_2O_3 glass according to claim 4 or 7, wherein the SiO_2-B_2O_3-based glass is a powder in the range of m. 9. The method for producing SiO_3-B_2O_3 glass according to claim 4, wherein the heat melting is flame melting.